The present invention relates to an improved aluminum alloy forming sheet having a high strength and further to a method for producing the same.
In the field of can-making, forming materials having a strength and a formability at a satisfactory level have not been found to date, and so conventionally, in making a can or the like, for a beverage, food and other product, can body parts and can end parts have been respectively made of different materials according to the properties required for the respective parts.
Al-Mg alloys having a strength of nearly 40 kg/mm.sup.2, such as 5082 aluminum alloy, 5182 aluminum alloy and 5056 aluminum alloy, have been used as can end materials or the like.
Further, heat-treatable aluminum alloys, such as Al-Cu type alloy, for example 2011, 2014, 2017 or 2024 alloys; Al-Mg-Si type alloy, for example, 6066 or 6262 alloy; and Al-Zn-Cu-Mg type alloy, for example, 7001, 7075 7079 or 7178 alloy are well-known as aluminum alloy materials having a strength exceeding 40 kg/mm.sup.2.
However, the above aluminum base alloys are difficult to work from ingots into sheets and are poor in the forming property.
Further, alloy materials containing much Cu have a poor corrosion resistance. When the above heat-treatable aluminum alloys are subjected to heat treatments such as solution treatment or aging, conditions of these heat treatments must be carefully and strictly controlled.
Still further, these heat-treatable aluminum materials are poor in spinning and ironing properties, and similar properties required in can-making, and further, cracks, clouding and mottling occur during spinning or ironing operations and the surface appearance of the formed material is considerably impaired.
Generally, 3004 alloy has been used as a can body material, but the amount of reduction in thickness is limited to a low degree because of insufficient strength.